Hmm, couldn't that example be simplified to:

  SetUpdatedToNow
  - set %content.updated% as %now% in the file "file.txt"

The whole reading and writing feels like a leftover from the days of programming. Reading it in, modifying and then writing assume it fits in memory, leaves out ideas around locking, filesystem issues, writing to a temp and swapping, etc. Giving the actual intent lets the LLM decide what is the best way which might be reading in , modifying and then writing.